Flux growth of β-NaGaO2 single crystals

The flux growth of ternary wurtzite β-NaGaO2 single crystals by slow cooling from 1300 °C using 20B2O3-80PbO as a flux was investigated. The β-NaGaO2 single crystals were successfully obtained from a starting solution of 0.075 mol of Na2CO3 and 0.0375 mol of Ga2O3 in 0.14 mol of 20B2O3-80PbO. Unlike the flux growth of β-LiGaO2 single crystals where the crystals exhibit preferential growth along the [0 0 1] direction, the obtained β-NaGaO2 crystals did not show preferential growth along any direction. The β-NaGaO2 single crystals were subjected to an ion exchange of the Na+ ions with Cu+ and Ag+ ions to respectively obtain β-CuGaO2 and β-AgGaO2, which have recently attracted attention as narrow-band-gap oxide semiconductors. However, the β-CuGaO2 was pulverized and the β-AgGaO2 exhibited many cracks caused by the large volume change created by the phase transformation induced during the ion exchange.